Container for receiving head shrinking film and method for forming a spill-resistant cover therefor

ABSTRACT

A device for heat shrinking thin film onto open-topped containers to form spill-resistant covers is shown. A radiant energy source is intermittently energized in association with timers to direct radiant energy towards the thin film. An energy absorbing body is associated with the thin film to absorb energy and create heat adjacent to the film which in turn causes the thin film to shrink. The energy absorbing body can be the adaptation of the thin film to be opaque to the radiant energy by either being coated with an energy absorbing coating such as printing, or being made partially opaque by means of tinting. The container can also be adapted to absorb energy by including a darkened band adjacent the upper edge of the rim. The device can also interpose an energy absorbing body, such as a darkened aluminum screen adjacent to the film to be heated to cause the thin film to shrink. The device shrinks the thin film around the rim first, then shrinks the film across the top of the container to form a spill-resistant cover. In one embodiment, printed patterns on the film can be used to create perforations.

This is a continuation of application Ser. No. 07/873,844 filed Apr. 27,1992, now U.S. Pat. No. 5,249,410.

FIELD OF THE INVENTION

This invention relates to a device which may be used to seal food intoopen-topped containers, to a method of sealing such containers and to aspecific type of open-topped container. In particular, this inventionrelates to a device suitable for heat shrinking film onto suchopen-topped containers to seal food or drink inside the container.

BACKGROUND OF THE INVENTION

Presently in the fast food drink industry it is typical to serve a drinkin a paper, plastic or other disposable cup topped with a preformedplastic lid. The plastic lid fits tightly over the lip formed at the topof, for example, a paper drink cup, and may include apertures to permitstraws or openings to be formed in the lid to directly drink thecontents of the cup.

Unfortunately, there are many problems associated with the use of theseplastic lids. For example, the lids are generally expensive. Further,the lids are bulky and create problems in storage and in disposal.Further, the seal formed by the lids is dependant upon the lid beingplaced on properly, and can leak if not properly placed. Finally, thehandling of the lid is not completely hygienic.

In order to overcome these problems, various devices and methods havebeen proposed in which a cover is placed on an open-topped container andthen heated to shrink it into sealing engagement with the top of such acontainer. Examples of such devices can be found in the following UnitedStates patents: U.S. Pat. Nos. 3,260,775; 3,354,604; 3,460,3173,491,510; 3,494,098; 3,507,093; 3,621,637; 3,877,200; 3,838,550;3,916,602; 4,035,987; 4,184,310 and 4,562,688. While the solutionsproposed by these prior devices and methods are interesting, they failto provide a sufficiently cost efficient, easy and inexpensivealternative to preformed rigid plastic lids. As a consequence, rigidplastic lids remain in widespread use. Some of the main failings ofthese prior devices are that they are bulky, noisy, unresponsive, andexpensive. Heating systems comprising blowing air over a hot element andthen onto a film require large amounts of unnecessary heat, even when instandby mode, which makes temperature control very difficult. Further,continuous elevated temperatures are expensive to maintain and may bedeleterious to the immediate environment.

SUMMARY OF THE INVENTION

Aside from the benefits of increased hygiene and reduced waste, thepresent invention is directed to providing a practical device which hascommercial utility. One aspect of the present device is to provide anenergy efficient way of sealing open-topped containers which avoids anysubstantial build-up of heat. An intermittent source of radiant energyis used, and energy is directed onto an energy absorber located at thespecific place where heat is required. Thus, heat is originated where itis needed, when it is needed and a cooler, quieter, safer and moreefficient device results.

The present invention provides a device for heat shrinking a cover ontoan open-topped container, said device comprising:

a housing adapted to receive said container; and having a strip of heatshrinkable thin film;

a cutting means positioned against said thin film for cutting said thinfilm upon said thin film being urged onto said cutting means by saidcontainer;

a hood for holding a cut piece of said film in place across said opentop of said container, wherein said cut piece includes a portionextending from under said hood downwardly around an upper outer rim ofsaid container;

a first radiant energy source for directing energy toward saiddownwardly extending portion of said cut piece of film;

a first means to absorb radiant energy to transfer heat to saiddownwardly extending portion of said cut piece of film; and

a switch means for intermittently energizing said first radiant energysource whereby said downwardly extending portion of said cut piece offilm is shrunk onto said rim;

The present invention also provides for a container for receiving heatshrinking film to form a spill-resistant cover comprising an open-toppedcontainer having a circumferential darkened band around said container,said darkened band having an elevated rate of absorption of radiantenergy over and above the rate of absorption of said container.

In a further embodiment the present invention provides a method offorming a spill-resistant cover on a container having an open top, themethod comprising placing a heat shrinkable thin film over the open topof said container, and subjecting said container and said thin film to asource of radiant energy wherein said radiant energy causes said thinfilm to shrink and form a spill-resistant cover over said open top ofsaid container.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a device according to the presentinvention in use;

FIG. 2 is a front sectional view of an open-topped container accordingto the present invention with a heat shrunk cover in place;

FIG. 2a is a top view of the container of FIG. 2.

FIG. 3 is a front view of the container of FIG. 2 having a darkenedupper band;

FIG. 4 is a top view of the device of FIG. 1, with the top wall brokenaway to show the contents;

FIG. 5 is a sectional view taken along lines 5--5 of FIG. 4;

FIG. 6 is a view similar to FIG. 5 with the container in a raisedposition;

FIG. 7 is a view of a part of the device of FIG. 1; and

FIG. 8 is a view along lines 8--8 of FIG. 7;

FIG. 9 is an alternate configuration for a knife element shown in FIG.5;

FIG. 10 is a view along lines 10--10 of FIG. 9;

FIG. 11 is a schematic sketch of an electronic control circuit for thepresent invention;

FIG. 12 is an alternate embodiment of a microswitch system according tothe present invention;

FIG. 13a is a view along lines 13--13 of FIG. 12 in a first position;and

FIG. 13b is a view along lines 13--13 of FIG. 12 in a second position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a device 10 for heat shrinking a thin film onto anopen-topped container 12. The housing 10 includes an opening 14 ofsufficient size to allow placement of the container 12 within thehousing 10. In the embodiment of FIG. 1, placement of the container 12within the opening 14 is accomplished manually, illustrated by a hand16.

Turning to FIG. 5, there is shown a cross-sectional schematic view ofthe operational components of the device 10 of FIG. 1. The container 12is shown in the opening 14. The opening 14 is defined by side walls 18and 20 of the device 10. Shown on the right-hand side is a roll of thinplastic film 22 on an axle 24. The film 26 passes over a roller 28across the top of the container 12 across a second roller 30 and onto atake-up axle 32. Shown at 34 is a rewind motor. It will be appreciatedthat the rewind motor 34 can rotate the pick-up axle 32 in the directionof arrow 36 which will advance the film 26 across the top of thecontainer 12 and cause the roll of film 22 to rotate in the direction ofarrow 38. Alternatively, the advancing of the film 26 could beaccomplished manually by turning a lever or knob mounted on take-up axle32.

The film 26 is preferably a bi-axially oriented shrink film having apreferred thickness of between 40 to 120 gauge with the most preferredbeing between 60 to 100 gauge. Good results have been achieved with a 75gauge polyvinyl chloride film purchased from Reynolds Metals Company atRichmond, Va. Other films, such as copolymers, polyolefins and the likemay also be appropriate. The film, to be most useful, must be foodgradecontact-approved by the appropriate regulatory authorities. A 71/2"outer diameter roll of 75 gauge shrink film, which includes a 3"diameter fibre core, will yield approximately 8,000 covers according tothe present invention.

In FIG. 5, the container 12 is located in a locator identified generallyat 40. The locator 40 is shown in more detail in FIGS. 7 and 8. Turningto FIG. 7, there is shown a plate 42 having a pair opposed guides 44 and46. The plate 42 also has an opening 48 located between the guides 44,46. The guides 44 and 46 are substantially identical and therefore thefollowing discussion in respect of guide 44 applies equally to guide 46.

The guide 44 comprises a rub rail 50 which contacts an outer edge of acontainer 12. Extending from plate 42 are two posts in respect of eachguide 44, 46. In respect of guide 44 there is a stop post 52 and a guidepost 54. A slot 56 is formed in the guide 44 and a spring 58 is housedbetween the guide post 54 and the end of the slot 56. A pin 59 may beused to secure one end of the spring 58. A washer 60 is used to retainthe other end of the spring 58 within the slot 56. The washer 60 isplaced around the guide post 54. Between the free end 55 of guide post54 and the washer 60 is a further spring 61. The spring 61 allows theguide plate 44 to articulate away from the plate 42 to facilitateremoval of the container 12 from the device 10.

It will now be appreciated that the guide 44 can move laterally in thedirection of double ended arrow 62 guided by means of the stop 52 andthe guide post 54 with the slot 56. It will also be appreciated that thecurved portion 64 of the rub rail 50 will provide an indication toanyone inserting a container 12 into the locator that the container isappropriately located. Appropriately in this sense means centered underthe plate opening 48.

Turning to FIG. 8, the locator 40 of FIG. 7 is shown in cross-sectionalview. As can be seen, the guides 44 and 46 are positioned on adjacentside edges of a container 12. The plate opening 48 is shown togetherwith the plate 42. The thin film 26 is also shown stretched across thetop 13 of the container 12.

It can now be appreciated that the container 12 can be moved in thedirection of double ended arrow 65 into position beneath plate opening48. During this period, the guides 44 and 46 will gradually open andthen close about the periphery of the container 12. Thereafter, as shownin FIG. 8, the container 12 is free to be moved in the direction ofdouble ended arrows 66 as will be discussed below. It will beappreciated that containers 12 of varying diameter can thus beaccommodated by the instant invention, since all containers will becentered by the locator beneath the plate opening 48. This is desirablein a food services environment where cup size selections typicallyinclude small, medium and large.

Turning now to FIG. 5, a container 12 is shown centered in locator 40. Afirst radiant energy source 68 and a second radiant heater 70 can now beexplained. Located above the centered and located container 12 is a topshrink hood 72. The second radiant heater 70 is located within the topshrink hood 72. The top shrink hood 72 includes a glass shield 74 and aheat transfer means 76. In some circumstances the glass shield 74 maynot be required, however, to prevent the possibility of splashesreaching the second radiant energy source 70, it is preferred. It maynot be necessary to use glass. Plastic or other transparent substancesmay be appropriate. Good results have been achieved when the heattransfer means 76 is made from a screen aluminum material painted a darkcolour, such as black. The dark aluminum heats and cools quickly whichis desirable in the circumstances.

A pierce tool 78 is also shown extending outwardly from the heattransfer means 76. The purpose of the pierce tool 78 is to make a ventopening in the thin film to allow gases such as carbon dioxide from asoft drink to escape the container.

An alternative to pierce tool 78 is to form small opaque portions 79 inthe shrink film. These opaque portions or "dots" will cause a hot pointwhich may perforate the film as more fully explained below. If desiredthe hot points can be made in a specified pattern to form a sippingopening or the like, as shown in FIG. 2A. Also shown in FIG. 2 is astraw 122 with a pointed end 124 for piercing the film, shown in placeas 126. A fluid, such as a soft drink is shown at 128.

Also shown in FIG. 5 is a drive belt 80 which connects a pulley 82 witha motor. Attached to the pulley 82 are a pair of arms 84. The arms 84rotate when the pulley 82 is rotated by the belt 80. Depending from thearms 84 about pivot points 86 are pivot arms 88. Pivot arms 88 include aroller 90 at one end and the first radiant energy source 68 at the otherend. If preferred, a reflector may be provided such as 92 around thefirst radiant energy source 68.

Also show in FIG. 5 is a knife or film cutting blade 94 to which isattached a heating element 96. The heated blade 94 ensures a quick cleancut of the thin film, upon the thin film contacting the blade 94. As canbe seen from FIG. 5, the blade 94 is below the top hood 72, so the filmwill be cut to shape just prior to or about the same time as thecontainer 12 contacts the hood 72. Good results have been achieved whenthe blade is made from a two point center face steel cutting rule, andmaintained at a temperature of between 275° F. to 400° F. This formatappears to limit smoke and fume generation.

The knife 94 may be circular in shape to provide a symmetrical overhangfor a circular container, or may be as shown in FIGS. 9 and 10. It willbe noted that the knife 94 in FIGS. 9 and 10 includes a rounded oblongsection 95. This will result in a similarly shaped section being formedin a cut piece of film, as described below, which can be used as aconvenient pull tab for removing a cover which has been shrunk onto acontainer 12. In the preferred embodiment the thin film 26 has a widthgreater than the width of the knife 94 so that a trim 27 (see FIG. 5) isleft after the cut is made, and the trim 27 is strong enough to allowthe film 26 to be advanced by a tensile force without tearing.

Turning now to FIG. 6, the operation of an instant device can now beunderstood. In FIG. 6 the container 12 has been raised in the directionof arrow 100. This has had the effect of pushing the film 26 upwardlyinto engagement with the knife heated film cutter blade 94. This hascaused a cut portion of the film shown as 102 to be draped across thetop 13 of the container 12. At this point the hood 72 is holding the cutpiece of film 102 generally in place. As the container 12 is raisedfurther, the hood 72 is also raised. Rollers 90 then contact a ledge 104formed on the outer surface of the hood 72. Further upward movementcauses the movement of the first radiant energy source 68 about thepivot point 86 until the first radiant energy source 68 is closelyadjacent to a draped over edge of cut portion 102 shown as 103. Contactis then made at a limit switch, as explained below in respect of FIG.11, which energizes a motor 99 (shown in FIG. 4). Upon energization ofthe motor 99, the belt 80 revolves causing the rotating arms 84 torevolve rotating the first radiant energy source 68 about the peripheryof the top of the container 13. Simultaneously with the energization ofthe motor 99 and the rotation of the first radiant energy source 68, thefirst radiant energy source 68 is energized to cause radiant energy tobe directed towards the dangling edge 103 of the cut portion 102 of thesaid film 26.

It will be appreciated that the preferred invention causes the firstradiant energy source 68 to move into position closely adjacent thedownward edge 103 of the cut portion 102. Such movement is preferredbecause radiant energy obeys the inverse squared rule in which theamount of energy is proportional to an inverse of the square of thedistance from the source. By locating the first radiant energy source 68close prior to being energized, more energy can be usefully used andfocused away, for example, from an operator's hands. Also, by thepivoting action, the operator's hands are kept clear of the energysource 68, until the container 12 is in position.

After a predetermined length of time, the first radiant energy source 68is de-energized and the second radiant energy source 70 is energized bya timer as described in more detail below. The second radiant energysource 70 energy is directed through the glass shield 74 onto an energyabsorbing body 76. This transfer of heat causes a shrinking of the topportion across container 12 of the cut portion 102. Thereafter, thesealed container 12 can be lowered and removed from the apparatus.

A preferred type of energy absorbing body 76 is a darkened aluminumscreen. The body 76 is placed very closely adjacent the top portion ofthe cut section 102 and may be in contact therewith. The darkened screenor body 76 absorbs energy and transfers it onto the top portion. It willbe appreciated that aluminum is a suitable material because it will coolrapidly, when the energy source 70 is shut off, thereby preventingpremature shrinkage of a top portion on a subsequent container uponbeing first introduced into the hood 20.

It has been found that the preferred radiant energy sources are TungstenHalogen Lamps. About 70% of the energy produced by these lamps is in thepreferred wavelength range of the infrared (750 millimicrons andbeyond).

These lamps are compact, durable, inexpensive and readily available.Lamps in the range of 200 to 300 watts are suitable. It will beappreciated by those skilled in the art that other energy sources whichproduce sufficient infrared radiant energy may also be used.

It is also to be noted that the radiant energy emitted by such an energysource can be turned on and off instantaneously and focused and directedto the location it is desired, without stray heat energy being produced,and the energy source does not have to be on continuously, or on standbyin readiness for a container, which is the case of prior art hot airsystems.

Turning now to FIG. 4, the belt 80, pulley 82 and drive motor 99 are allshown. Also are shown two rotating arms 84 and two first radiant heaters68. It will be appreciated by those skilled in the art that fewer ormore radiant heating elements could be used according to spacerequirements and preference. However, when the drive motor operates at100 rpm, two radiant heat means 68 provides good results. By varying thesize of the pulley 82, the speed of revolution of the first radiantenergy source 68 can also be varied. Good results have been achievedwhen the pully 82 is configured to cause the first radiant energy source68 to rotate at 100 rpm.

It will also be appreciated that the spinning first radiant energysource 68 could be replaced with a row of fixed position bulbs. However,the process would be slightly more difficult to control, since the totalenergy output would likely be greater, and more energy expensive. Thus,the moving first energy source 68 is preferred.

Turning to FIG. 11, a schematic of an electrical system 150 for theinstant invention is disclosed, which sets out in more detail theinteraction between the container 12 and hood 72 location, and theactivation of the various components described above.

One of the characteristics of the electrical design is that it mustcompensate for the varying rates that the container 12, which is movedby a human hand, enters and leaves the device 10.

In the preferred embodiment the raising and lowering of hood 72 and themotion of locator 40 will trigger micro-switches which engage timers asdescribed below. Certain events must take place as hood 72 is raised andother events must take place when hood 72 is lowered.

Referring to the wiring system 150, F1 is a fuse. When the main switch170 is turned on, a pilot light R lights up. Then, switches S1 and S2are manually turned on. As shown, S1 turns on resistance heater 96,which heat the knife 94. A thermostatic control is shown at 97. When S2is turned on, it activates motor 99 and also signals timer T1. Alsoshown is a relay TM-1. The timer T1 engages motor 34 and advances thefilm 26 for a single "space", which is determined by the time set ontimer T1. Thus when the machine is activated and ready to operate byturning on switch S2, a fresh piece of film 26 is automaticallypresented. Switch LS1 is situated on plate 42, (shown in ghost outlinein FIG. 7) so that when guide 46 rotates outwardly on withdrawal of thecontainer, LS1 also signals timer T1 which engages motor 34 and advancesthe film in a like manner.

Also shown are switches LS2 and LS3 which close when hood 72 movesupward. These switches activate a second timer T2 which activates relayTM-2 which in turn activates first radiant energy source 68. On thedownward motion switch LS3 opens and thereby prevents timer T2 fromactivating source 68 again.

On the downward motion of hood 72, switch LS4 closes, which activatestimer T3 which through a relay TM-3, activates radiant energy source 70for a predetermined time.

FIG. 12 shows in schematic form the microswitch interconnections. On theleft hand side of FIG. 12 are the belt 80 around the pulley 82. A shaft200 extends upwardly from the top hood 72. A connecting rod 202 isattached to shaft 200, and will rise and subside with the hood 72 beingraised and lowered. Remote from shaft 200 there is a rack 204 connectedto the rod 202 which interacts with a pinion 206, in a manner shown bydouble ended arrows 208. Also shown are a cam shaft 210 attached toeccentric cams 212.

Shown in FIGS. 13A and 13B are the means of closing electrical circuitsupon rotation of the cam shaft 210 by the pinion 206. A secondary roller214 is located on a pivot arm 216. When cam 212 is rotated in onedirection an electrical spring clip 218 is forced into contact with anelectrical contact 220 closing a circuit. Upon being rotated in anopposite direction, the cam 212 urges the pivot arm 216 up and out ofthe way, and does not close the circuit, as shown in FIG. 13B.

It can now be appreciated that the present invention uses radiant energyfrom the radiant energy sources to effect shrinkage. Radiant energy ispreferred, because it travels relatively unimpeded through transparentmediums such as air or transparent film. The preferred radiant energysource is a Tungsten-Halogen bulb, which is described in more detailabove. The present invention has process parameters for heating whichdepend upon an absorbing means for the radiant energy, and inparticular, how close any absorbing means conforms to a theoreticallyideal "black body". An ideal "black body" completely absorbs all radiantenergy that strikes it and thus is capable of radiating that same energyoutward.

The way in which the present invention seals heat shrinkable thin filmonto a container, is to employ a first means to transfer heat to thedownwardly extending portion of the cut piece of thin film. In thissense, the first means can comprise adapting the thin film to absorbenergy, interposing an absorbent body adjacent to thin film, or adaptingthe area of the container just below the rim to become energy absorbing.The thin film can be adapted to absorb energy by being made from atinted material, or by being coated with an energy absorbent coating,for example, printing. The ability of the opaque or coated film toabsorb radiant energy will vary depending upon what type of tinting orcoating is used. A darker or more opaque film will absorb more energy.

An example of a preferred interposed absorbent body is a darkenedaluminum screen 112, which moves closely adjacent the edge 103. Thedarkened portion of the screen will absorb energy and then radiate it,giving rise to heat. The heat will be transferred to the air adjacent tothe film, then to the film which will shrink the film.

The container may be adapted to absorb radiant energy, and thus produceheat in a preferred location, by including a darkened band 15 in thearea where heat generation is desired, such as just below the rim. Foraesthetic reasons, black bands may not be acceptable, but other colouredbands will also work. With a cooler colour, the exposure to the radiantenergy source may need to be slightly longer. However, the length oftime of exposure to the radiant energy source can be adjusted in thepresent invention through adjustments made to the timer T2. A gap 17 maybe incorporated into the band 15 to permit the end user to lift theshrunken cover off the container if so desired.

In some circumstances, it may be desirable to urge the film onto thecup. Therefore, the present invention also comprehends the use of aspring wire 110, which trails (or leads) the revolving first radiantheat means 68, and urges the edge 103 into contact with the container 12just below the top 13.

It will be appreciated by those skilled in the art that the foregoingdescription relates to a preferred embodiment and that variousmodifications can be made without departing from the broad scope of theappended claims. Some of these modifications have been discussed aboveand others will be apparent to those skilled in the art.

We claim:
 1. A method of forming a spill resistant top cover on acontainer having an open top, using a device having a radiant energysource, the method comprising:selecting a heat shrinkable thin film madefrom generally transparent plastic; adapting at least a portion of saidheat shrinkable thin film to become more absorbent to radiant energythan a transparent thin film; manually positioning said containerrelative to said device wherein said more absorbent portion can beexposed to said source of radiant energy; and placing said heatshrinkable thin film over the top of said container wherein said moreabsorbent portion hangs over an upper side edge of said container,subjecting said more absorbent portion of said heat shrinkable thin filmto said source of radiant energy wherein said more absorbent thin filmabsorbs said radiant energy, creating heat, which causes said thin filmto shrink around said rim and form a spill resistant cover over saidopen top of said container.
 2. A method as claimed in claim 1 whereinsaid container is subjected to a first source of radiant energy causingsaid thin film in contact with said container to shrink around said opentop, followed by subjecting said container to a second source of radiantenergy causing said thin film across said top of said container toshrink.
 3. A method as claimed in claim 2 wherein said first and saidsecond radiant energy sources are activated intermittently.
 4. A methodas claimed in claim 3 wherein said first and said second radiant energysources are controlled by a timer and activated only when required toheat shrink said thin film.
 5. A method as claimed in claim 4 furthercomprising the step of focusing said first and said second energysources onto the portions of said thin film to be heat shrunk withoutsignificant stray energy produced.
 6. A method as claimed in claim 5wherein said first radiant energy source is rotated around said top ofsaid container to heat shrink said thin film onto said container.
 7. Amethod as claimed in claim 6 wherein said thin film is prepared withopaque portions in a defined pattern, said opaque portions of said thinfilm being heated to a higher temperature than surrounding portions ofsaid thin film when subjected to radiant energy creating hot pointswhich may perforate said thin film to form a sipping opening.
 8. Amethod as claimed in claim 7 further comprising the step of cutting anoblong section in said thin film to be placed over said open-toppedcontainer, said oblong section extending beyond said open top of saidcontainer and acting as a pull tab for removing said thin film aftersaid thin film has been heat shrunk.
 9. A method as claimed in claim 8wherein said first and second radiant energy sources are sources ofinfrared energy.
 10. A method as claimed in claims 1, 5 or 9 furthercomprising the step of piercing the heat shrunk thin film across the topof said container to provide a vent opening allowing internal gaseswithin said container to escape.
 11. A method as claimed in claims 1, 5or 9 wherein said sources of radiant energy are tungsten halogen lamps.12. A method as claimed in claims 1, 5 or 9 further comprising adaptingthe portion of said container in contact with said thin film to absorbradiant energy.
 13. A method as claimed in claim 1 wherein said step ofselectively adapting said film to be opaque to radiant energy comprisesprinting a pattern on said film when said pattern is comprised of amaterial which is opaque to said radiant energy.
 14. A method as claimedin claim 2 wherein said method of selectively adapting said filmcomprises tinting said film.
 15. A method as claimed in claim 14 or 13wherein said method of selectively adapting said film results in saidfilm being more opaque to said radiant energy and thus more easilyshrunk upon being exposed to infrared radiation.